A semiconductor nanowire refers to a semiconductor wire having transverse lateral and vertical dimensions of the order of a nanometer (10−9 meter) or tens of nanometers. Typically, the transverse lateral dimension and the vertical dimension are less than 20 nm but can be as large as 100 nm.
The limitation on the lateral dimension applies to the transverse lateral dimension (the width) and the vertical lateral dimension (the height). The longitudinal lateral dimension (the length) of the semiconductor nanowire is unlimited, and may be, for example, from 1 nm to 1 mm. (The preferred length is less than 1 um) When the lateral dimensions of the semiconductor nanowire is less than tens of nanometers, quantum mechanical effects may become important. As such, semiconductor nanowires are also called semiconductor quantum wires.
The transverse lateral dimension of a semiconductor nanowire is currently sublithographic, i.e., may not be printed by a direct image transfer from a photoresist that is patterned by a single exposure. As of 2008, the critical dimension, i.e., the smallest printable dimension that may be printed by lithographic methods, is about 35 nm. Dimensions less than the critical dimension are called sublithographic dimensions. At any given time, the critical dimension and the range of the sublithographic dimension are defined by the best available lithographic tool in the semiconductor industry. In general, the critical dimension and the range of the sublithographic dimension decreases in each successive technology node and established by a manufacturing standard accepted across the semiconductor industry.
The charge transport property of a semiconductor nanowire is controlled by the charge carriers present in the semiconductor nanowire. A higher density of free charge carriers in the semiconductor nanowire increases the conductivity of the semiconductor nanowire, while a low density of free charge carriers in the semiconductor nanowire decreases the conductivity of the semiconductor nanowire.